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Title 

A zymogen form of masquerade-like serine proteinase homologue is cleaved during pro-phenoloxidase activation by Ca2+ in coleopteran and Tenebrio molitor larvae

Authors 

K Y LeeR ZhangM S KimJ W ParkHo Yong ParkS I KawabataB L Lee

Publisher 

Federation of European Biochemical Societies

Issue Date 

2002

Citation 

European Journal of Biochemistry, vol. 269, no. 17, pp. 4375-4383

Keywords 

innate immunityinsectmasqueradepro-phenoloxidaseserine proteinase homologuebeta 1,3 glucancalcium ioncomplementary DNAmonophenol monooxygenaseproteinase

Abstract 

To elucidate the biochemical activation mechanism of the insect pro-phenoloxidase (pro-PO) system, we purified a 45-kDa protein to homogeneity from the hemolymph of Tenebrio molitor (mealworm) larvae, and cloned its cDNA. The overall structure of the 45-kDa protein is similar to Drosophila masquerade serine proteinase homologue, which isan essential component in Drosophila muscle development. This Tenebrio masquerade-like serine proteinase homologue (Tm-mas) contains a trypsin-like serine proteinase domain in the C-terminal region, except for the substitution of Ser to Gly at the active site triad, and a disulfide-knotted domain at the amino-terminal region. When the purified 45-kDa Tm-mas was incubated with CM-Toyopearl eluate solution containing pro-PO and other pro-PO activating factors, the resulting phenoloxidase (PO) activity was shown to be independent of Ca2+. This suggests that the purified 45-kDa Tm-mas is an activated form of pro-PO activating factor. The 55-kDa zymogen form of Tm-mas was detected in the hemolymph when PO activity was not evident. However, when Tenebrio hemolymph was incubated with Ca2+, a 79-kDa Tenebrio pro-PO and the 55-kDa zymogen Tm-mas converted to 76-kDa PO and 45-kDa Tm-mas, respectively, with detectable PO activity. Furthermore, when Tenebrio hemolymph was incubated with Ca2+ and β-1,3-glucan, the conversion of pro-PO to PO and the 55-kDa zymogen Tm-mas to the 45-kDa protein, was faster than in the presence of Ca2+ only. These results suggest that the cleavage of the 55-kDa zymogen of Tm-mas by a limited proteolysis is necessary for PO activity, and the Tm-mas is a pro-PO activating cofactor.

ISSN 

0014-2956

Link 

http://dx.doi.org/10.1046/j.1432-1033.2002.03155.x

Appears in Collections

1. Journal Articles > Journal Articles

Registered Date

2017-04-19


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